Mingo is the same way, but it's because I taught him not to jump on my arm unless I have a long-sleeved shirt on. I got scratched too much in short sleeves. He's very polite about it - if I invite him in a 3/4 sleeve, he eyes my arm, then looks up to see if it's all right. I think it's harmless, too, and he loves to do it. As soon as I start to dress or undress, he's on the bed, softly mewing. It means a lot to him.